Use of crosslinked copolymers of monoethylenically unsaturated carboxylic acids as stabilizer in oil-in-water emulsions

ABSTRACT

The use of crosslinked copolymers obtainable by precipitation polymerization of monomer mixtures comprising 
     (a) monoethylenically unsaturated C 3 -C 8 -carboxylic acids, their anhydrides or mixtures of said carboxylic acids and anhydrides, 
     (b) compounds with at least 2 non-conjugated ethylenic double bonds in the molecule as crosslinkers and, where appropriate, 
     (c) other monoethylenically unsaturated monomers which are copolymerizable with monomers (a) and (b), 
     in the presence of free-radical polymerization initiators and from 0.1 to 20% by weight, based on the monomers used, of saturated, nonionic surface-active compounds, as stabilizer in oil-in-water emulsions in amounts of from 0.01 to 5% of the weight of the emulsions, and cosmetic and pharmaceutical formulations based on oil-in-water emulsions which contain said precipitation polymers.

The present invention relates to the use of crosslinked copolymers whichare prepared by precipitation polymerization of monomer mixturescomprising

(a) monoethylenically unsaturated C₃-C₈-carboxylic acids, theiranhydrides or mixtures of said carboxylic acids and anhydrides,

(b) compounds with at least two non-conjugated ethylenic double bonds inthe molecule as crosslinkers and, where appropriate,

(c) other monoethylenically unsaturated monomers which arecopolymerizable with monomers (a) and (b), in the presence offree-radical polymerization initiators and certain surface-activecompounds, and to cosmetic or pharmaceutical formulations based onoil-in-water emulsions containing the abovementioned crosslinkedcopolymers as stabilizer.

DE-B-1 138 225 discloses a process for preparing water-insoluble,water-swellable copolymers by precipitation polymerization ofmonoethylenically unsaturated carboxylic acids, monomers with at leasttwo non-conjugated ethylenic double bonds in the molecule ascrosslinkers and, where appropriate, other water-insolublemonoethylenically unsaturated monomers in the presence of free-radicalpolymerization initiators and of protective colloids and/or emulsifierswhich are soluble both in organic solvents and in water. Thus, forexample, precipitation polymerization of acrylic acid and butanedioldiacrylate in 1,2-dichloroethane in the presence of polyvinyl etherresults in a fine powder which, in ammonia-containing water, forms stiffgels which are suitable as ointment bases for cosmetics. The crosslinkedpolymers are used in particular as swelling or thickening agents.

DE-A-2 949 843 discloses a process for preparing crosslinked polymers ofmonoethylenically unsaturated carboxylic acids by free-radicalprecipitation polymerization of the monomers in the presence offree-radical polymerization initiators and homopolymers ofvinylpyrrolidone as protective colloid. The precipitation polymers areused as thickeners in the drugs, cosmetics, paper, textiles, adhesivesand emulsion paint sectors.

In the process discosed in DE-A-2 833 468, for example, copolymers ofacrylic acid or methacrylic acid and acrylic esters or methacrylicesters are subjected to precipitation polymerization in the presence ofethylene/propylene rubber where appropriate in the presence ofcrosslinkers. The fine-particle polymers obtainable in this way are usedas thickeners in printing pastes, paper coatings and aqueous paintemulsions.

U.S. Pat. No. 4,419,502 discloses the polymerization ofmonoethylenically unsaturated carboxylic acids in the presence ofcrosslinkers, free-radical polymerization initiators and polyoxyethylenealkyl ethers and/or polyoxyethylene sorbitan esters in methylenechloride. The surfactants which are also used in the precipitationpolymerization serve to control the particle size of the polymers,improve the stirrability of the polymerization mixture and preventdeposits forming in the reaction vessel.

EP-A-0 268 164 discloses storage-stable, rapidly breaking oil-in-wateremulsions which comprise a copolymer of acrylic acid with a minorcontent of a long-chain alkyl acrylate as stabilizer. As stated on page8 of this citation, permanent stabilization of oil-in-water emulsions isnot possible by adding homopolymers of acrylic acid or slightlycrosslinked polyacrylic acids.

The earlier non-prior-published DE Application P 4213283.5 discloses theuse of copolymers of monoethylenically unsaturated carboxylic acids andlong-chain compounds with isolated CC multiple bonds and, whereappropriate, further copolymerizable monomers and crosslinkers asthickeners or dispersants, for example in cosmetic or pharmaceuticalformulations. The copolymers are prepared by precipitationpolymerization.

It is an object of the present invention to provide other stabilizersfor oil-in-water emulsions.

We have found that this object is achieved by using crosslinked polymersobtainable by precipitation polymerization of monomer mixturescomprising

(a) monoethylenically unsaturated C₃-C₈-carboxylic acids, theiranhydrides or mixtures of said carboxylic acids and anhydrides,

(b) compounds with at least two non-conjugated ethylenic double bonds inthe molecule as crosslinkers and, where appropriate,

(c) other monoethylenically unsaturated monomers which arecopolymerizable with monomers (a) and (b),

in the presence of free-radical polymerization initiators and from 0.1to 20% by weight, based on the monomers used, of saturated, nonionicsurface-active compounds, as stabilizer in oil-in-water emulsions inamounts of from 0.01 to 5% of the weight of the emulsions.

The present invention also relates to cosmetic or pharmaceuticalformulations based on oil-in-water emulsions which contain as stabilizerfrom 0.01 to 5% by weight of crosslinked polymers obtainable byprecipitation polymerization of monomers mixtures comprising

(a) monoethylenically unsaturated C₃-C₈-carboxylic acids, theiranhydrides or mixtures of said carboxylic acids and anhydrides,

(b) compounds with at least two non-conjugated ethylenic double bonds inthe molecule as crosslinkers and, where appropriate,

(c) other monoethylenically unsaturated monomers which arecopolymerizable with monomers (a) and (b),

in the presence of free-radical polymerization initiators and from 0.1to 20% by weight, based on the monomers used, of saturated, nonionicsurface-active compounds.

Suitable crosslinked copolymers are prepared by precipitationpolymerization of monomer mixtures. Component (a) used in the monomermixtures comprises monoethylenically unsaturated C₃-C₈-carboxylic acids,their anhydrides or mixtures of said carboxylic acids and anhydrides.Examples of suitable carboxylic acids are acrylic acid, methacrylicacid, maleic acid, fumaric acid, itaconic acid, crotonic acid and2-pentenoic acid. Examples of suitable anhydrides are methacrylicanhydride, maleic anhydride and itaconic anhydride. Monomers of group(a) which are preferably used are acrylic acid, methacrylic acid, maleicacid, maleic anhydride and/or methacrylic anhydride. Monomers (a) can bepresent, for example, in the mixtures used for the polymerization inamounts of from 50 to 99,99, preferably from 80 to 99,99, % by weight.

Suitable as monomer of group (b) are compounds with at least twonon-conjugated ethylenic double bonds in the molecule. Monomers of thistype are normally used as crosslinkers in polymerizations. They increasethe molecular weight of the resulting copolymers. Examples of suitablecrosslinkers are the diacrylates or dimethacrylates of glycols orpolyalkylene glycols, such as ethylene glycol diacrylate, ethyleneglycol dimethacrylate, diethylene glycol methacrylate, diethylene glycoldiacrylate or diacrylates or dimethacrylates of polyethylene glycolswith molecular weights of up to 2000, divinylbenzene, divinyldioxane,divinylethyleneurea, diallyltartaramide, methylenebisacrylamide,polyhydric alcohols which are esterified at least twice with acrylicacid or methacrylic acid, such as trimethylolpropane, pentaerythritol,1,4-butanediol, 1,6-hexanediol and sorbitol, trivinylcyclohexane,triallyltriazinetrione, allyl esters of acrylic acid and methacrylicacid, and allyl ethers of polyhydric alcohols, eg. the di- and triallylethers of trimethylolpropane, pentaerythritol, sorbitol and sucrose.Crosslinkers which are preferably used are pentaerythritol triallylethers, diacrylates or dimethacrylates of glycols or polyethyleneglycols with molecular weights of up to 2000, pentaallylsucrose, allylmethacrylate, trimethylolpropane diallyl ether and/ormethylenebisacrylamide. The amounts of crosslinker in the monomermixture are preferably from 0.01 to 20% by weight. In most cases, themonomer mixtures used for the polymerization contain from 0.1 to 2% byweight of crosslinker, it also being possible to use mixtures ofdifferent crosslinkers.

Examples are further monoethylenically unsaturated monomers of group (c)suitable for copolymerization with monomers (a) and (b) ofN-vinylpyrrolidone, N-vinylcaprolactam, C₁-C₁₈-alkyl (meth)acrylates,for example methyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate,n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, stearyl acrylate orstearyl methacrylate, acrylamide, methacrylamide,N-(C₁-C₈-alkyl)acrylamides or -methacrylamides such asN,N-dimethylacrylamide, N,N-dimethylmethacrylamide,N-tert-butylacrylamide, N-tert-butylmethacrylamide,N-tert-octylacrylamide or N-tert-octylmethacrylamide, vinyl esters ofsaturated C₁-C₈-carboxylic acids, such as vinyl acetate, vinylpropionate, vinyl butyrate or vinyl stearate, styrene, phenoxyethylacrylate, hydroxyalkylene monoacrylic esters and hydroxyalkylenemonomethacrylic esters with, in each case, 2 to 6 carbon atoms in thealkylene chain or acrylic esters and methacrylic esters of ethoxylatedC₁-C₁₈-alcohols, where from 2 to 25 ethylene oxide units have been addedper mol of alcohol. If the compounds of the group (c) are used to modifythe copolymers, their content in the monomer mixture is up to 49.89,preferably from 0 to 19.09, % by weight. Monomers of group (c) which arepreferably used are N-vinylpyrrolidone, C₁-C₁₈-alkyl (meth)acrylates,styrene, hydroxyethyl (meth)acrylate and ethyl diglycol acrylate.

The crosslinked copolymers to be used according to the invention areprepared in the presence of specific surface-active compounds. One groupof these surface-active compounds comprises saturated, nonionicsurfactants such as esters of sugars or sugar derivatives, such assucrose esters, mannose esters, xylose esters or sorbitan esters, estersand ethers of glycerol, polyglycerol or glycerol/sugar condensates,ceramides and glycosyl-ceramides, fatty acid alkanolamides such as fattyacid ethanolamides, fatty acid isopropanolamides, fatty aciddiethanolamides, fatty acid polydiethanolamides, N-alkylpyrrolidonederivatives, alkyl pyrrolidone-5-carboxylates, citric and tartaricesters, C₁-C₁₈-alkyl (poly)glycosides, hydroxyalkyl polyglycosides,fatty acid esters of polyhydroxy compounds such as trimethylolpropane,erythritol, pentaerythritol, neopentyl diglycol, triethanolamine orcondensates derived therefrom, alkoxylates, in particular the adducts ofethylene oxide and/or propylene oxide with the compounds listed above,and with oxo alcohols, C₈-C₃₀-alcohols, alkylphenols, fatty acid amides,fatty amines, fatty acids and derivatives such as hydroxy carboxylicacids, it being possible for the polyalkylene oxide chains to bemodified at one end or both ends. In the caes of modification at bothends, the modifying components can be identical or different and, forexample, in part also represent a C₁-C₄-ether functionality.

Polymeric surfactants which contain ethylene oxide and/or propyleneoxide units as hydrophilic part of the molecule are uncrosslinked andhave molecular weights of from 500 to 100,000, preferably 700 to 20,000.The polymeric surfactants may, besides at least one hydrophilic block,contain at least one hydrophobic block or are composed of a hydrophilicchain with hydrophobic branches arranged in the manner of a comb. Thehydrophilic part of the polymeric surfactants is formed by homopolymersof ethylene oxide or propylene oxide or of block copolymers of ethyleneoxide and propylene oxide and of block and comb polymers with blocks ofpolyethylene oxide, polypropylene oxide or polyco(ethylene oxide,propylene oxide), whereas the hydrophobic part of the polymericsurfactants comprises blocks of polystyrenes, polyalkyl (meth)acrylates,silicone oils, polyhydroxy fatty acids, polyamidoamines, polyisobutylsor polytetrahydrofurans. It is also possible for general polymers whichhave at least one amino group, a hydroxyl group which can bedeprotonated with bases, or an anionic group and have a molecular weightof from 100 to 5000 to be reacted with ethylene oxide, propylene oxideor mixtures thereof to give suitable polymeric surfactants.

Further surface-active compounds are sorbitan esters, sucrose esters orglycerol esters of saturated C₈-C₃₀-carboxylic acids or alkoxylationproducts of these esters. The abovementioned esters are preferablyderived from C₁₂-C₂₂-carboxylic acids. Alkoxylation products arepreferably the adducts of ethylene oxide with the esters. Up to 80 molof ethylene oxide can be added per mol of the suitable esters. Alsosuitable as surface-active compounds are adducts of ethylene oxide andpropylene oxide and/or butylene oxides with the esters.

Further saturated, nonionic surface-active compounds are hydrophobicallymodified cellulose and/or starch, such as ethylcelluloses,hydroxypropylmethylcelluloses, methylcelluloses, hydroxypropylcellulosesor cellulose triacetate.

The saturated, nonionic surface-active compounds of those mentionedabove which are preferably used are sucrose esters, sorbitan esters,glycerol esters, alkyl (poly)glycosides, adducts of ethylene oxide withthe abovementioned compounds and adducts of ethylene oxide withC₁₂-C₂₂-alcohols, and the use of sorbitan stearate, sorbitan monolaurateand hydrogenated castor oil ethoxylates is particularly preferred.

The above-described surfactants, as well as the polymeric surfactantsand modified celluloses and starches, are surface-active compounds. Theyconsist of a hydrophobic part and a hydrophilic part. When they havesufficient solubility in water, they have a surface tension measured in1% by weight aqueous solution against air of less than 66 mN/m at 20° C.

The above-described surface-active compounds are used in theprecipitation polymerization in amounts of from 0.1 to 20, preferably0.25 to 10, % of the weight of the monomers.

The precipitation polymerization is normally carried out in a solvent inwhich the monomers are soluble and the resulting polymers are insoluble.Examples of suitable solvents are aromatic and saturated aliphatichydrocarbons. Examples of aromatic hydrocarbons are benzene, toluene,xylene and isopropylbenzene. The saturated aliphatic hydrocarbonspreferably have from 5 to 12 carbon atoms. Pentane, pentane, n-hexane,cyclohexane, octane and isooctane are suitable. The precipitationpolymerization can also be carried out in halogenated saturatedaliphatic hydrocarbons such as 1,1,1-trichloroethane or methylenechloride. Also suitable as reaction medium are ethers, C₂-C₆-alkylesters of formic acid or acetic acid, ketones with from 3 to 6 carbonatoms, liquid or supercritical carbon dioxide. Examples of suitableethers are tert-butyl methyl ether and isobutyl methyl ether. The alkylesters of formic acid or acetic acid are preferably derived fromsaturated alcohols with from 2 to 6 carbon atoms, eg. ethyl formate,methyl acetate or ethyl acetate. Examples of suitable ketones areacetone and methyl ethyl ketone. The diluents can be used alone or mixedwith one another. The diluents preferably used in the precipitationpolymerization are saturated aliphatic hydrocarbons with from 5 to 8carbon atoms in the molecule, which can be straight-chain or branched,cyclic or bicyclic. Cyclohexane is particularly preferably used assolvent in the precipitation polymerization. The amount of solvent ischosen so that the reaction mixture can be stirred during thepolymerization. The solids content of the mixture after thepolymerization is preferably in the range from 10 to 40% by weight.

The molecular weight of the copolymers can, if required, be reduced byadding regulators to the polymerizing mixture. Examples of suitableregulators are mercapto compounds such as dodecyl mercaptan,thioethanol, thioglycolic acid or mercaptopropionic acid. If regulatorsare used, they are employed in amounts of from 0.1 to 5% of the weightof the monomers.

The copolymerization takes place in the presence of free-radicalpolymerization initiators. Suitable compounds of this type are azo orperoxo compounds, eg. diacyl peroxides such as dilauroyl peroxide,didecanoyl peroxide and dioctanoyl peroxide, or peresters such astert-butyl peroctanoate, tert-butyl perpivalate, tert-amyl perpivalateor tert-butyl perneodecanoate, and azo compounds such as dimethyl2,2′-azobis(isobutyrate), 2,2′-azobis(isobutyronitrile),2,2′-azobis(2-methylbutyronitrile) or2,2′-azobis(2,4-dimethylvaleronitrile). The initiators are used in theamounts customary in precipitation polymerization, eg. in amounts offrom 0.05 to 5% of the weight of the monomers. If water and/or bases arealso used in the precipitation polymerization, the amounts are only suchthat the mixture of all the components just appears homogeneous beforethe polymerization starts.

The precipitation polymerization is normally carried out under an inertgas atmosphere. The copolymerization can be carried out, for example, insuch a way that all the components present during the polymerization areintroduced into a polymerization vessel and the reaction is started, andthe reaction mixture is cooled where appropriate to control thetemperature. However, it is also possible to proceed in such a way thatonly some of the components to be polymerized are introduced, thepolymerization is started, and the remainder of the mixture to bepolymerized is metered in continuously or batchwise depending on theprogress of the polymerization. However, it is also possible to proceedin such a way that the diluent is initially introduced together with asurfactant, and the monomers and the polymerization initiator areseparately added thereto continuously or batchwise.

The temperature during the polymerization is generally from 40 to 160,preferably 50 to 120, °C. It can be controlled in various ways duringthe reaction by a program. The polymerization is preferably carried outunder atmospheric pressure but can also be carried out under reduced orelevated pressure. If the polymerization temperature is above theboiling point of the inert diluent, the polymerization is carried out inpressure-tight apparatus under pressures of up to 8 bar. If carbondioxide is used as inert diluent, the polymerization is normally carriedout in an autoclave above the critical temperature of carbon dioxide.The pressures are then above 73 bar.

The polymerization process is preferably controlled in such a way thatthe copolymer results in the form of a fine-particle powder. The averageparticle size of the polymer powder is from 0.1 to 500, preferably 0.5to 200, μm. After the polymerization, the crosslinked copolymer isseparated from the other components of the reaction mixture, for exampleby filtration, decantation or centrifugation. The resulting powder can,where appropriate, be subjected to further suitable separation, washing,drying or milling processes.

Particularly interesting precipitation polymers are those obtainable bycopolymerization of monomer mixtures comprising

a) 80-99,99% by weight of acrylic acid, methacrylic acid, maleic acid,maleic anhydride and/or methacrylic anhydride and

b) 0.01-20% by weight of pentaerythritol triallyl ether, diacrylates ordimethacrylates of glycols or polyethylene glycols with molecularweights of up to 2000, pentaallylsucrose, allyl methacrylate,trimethylolpropane diallyl ether and/or methylenebisacrylamide.

The resulting copolymers are crosslinked and insoluble in water, butthey swell in water.

The above-described copolymers are used as stabilizer in oil-in-wateremulsions in amounts of from 0.01 to 5% of the weight of the emulsions.They are suitable for stabilizing all oil-in-water emulsions, eg.water-in-oil polymer emulsions, antifoam agents based on oil-in-wateremulsions, textile printing pastes, paints, cleaner formulations, oilwell muds, liquid detergents and, in particular, for stabilizingcosmetic or pharmaceutical formulations based on oil-in-water emulsions.

In order to achieve permanent stabilization of oil-in-water emulsions,the dispersed polymer is neutralized sufficiently with a base. Examplesof suitable bases are alkali metal bases such as alkali metal hydroxidesand carbonates, for example NaOH, KOH and sodium and potassiumcarbonate, ammonia and organic amines, pyridines and amidines ormixtures thereof. On neutralization with organic amines, thosepreferably used are alkanolamines from the series of mono-, di- ortrialkanolamines with from 2 to 5 carbon atoms in the alkanol residuesuch as mono-, di- or triethanolamine, mono-, di- ortri(iso)propanolamine or 2-amino-2-methylpropanol, alkanediolamines withfrom 2 to 4 carbon atoms in the alkanediol residue such as2-amino-2-methyl-1,3-propanediol or 2-amino-2-ethyl-1,3-propanediol,alkanepolyolamines such as tris(hydroxymethyl)aminomethane orN,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine, alkylamines such asdi(2-ethylhexyl)amine, triamylamine or dodecylamine and amino etherssuch as morpholine.

The cosmetic or pharmaceutical formulations may moreover contain as oilany of the oils customarily used for this purpose. The total amount ofthe oil phase in the emulsion can be up to 80% by weight. The amount ofthe oil phase in the cosmetic or pharmaceutical formulations ispreferably from 10 to 50% by weight. The slightly crosslinked copolymersare preferably used to stabilize creams or lotions. They are also verysuitable for thickening aqueous systems or forming thickened gels afterthe dispersed copolymer has been utilized sufficiently by adding a base,eg. triethanolamine, sodium hydroxide solution, potassium hydroxidesolution, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol,diisopropanolamine or tetrahydroxypropylethylenediamine.

In contrast to slightly crosslinked homopolymers of acrylic acid, it ispossible with the slightly crosslinked copolymers to be used accordingto the invention to stabilize oil-in-water emulsions permanently. Theamount of crosslinked copolymers preferably used is from 0.05 to 2% ofthe weight of the emulsions.

EXAMPLES Determination of Gel Viscosity

1 g of a crosslinked copolymer and 200 g of water are weighed into a 300ml beaker and stirred until homogeneous. Then 1 ml of triethanolamine isadded, and the mixture is stirred until a homogeneous mixture isproduced. A Haake VT-02 manual viscometer with spindle 1 is then used todetermine the viscosity of the mixture at 20° C. and 60 rpm.

Polymer 1

1320 ml of cyclohexane, 50 g of acrylic acid, 1.5 g of pentaerythritoltriallyl ether, 7.5 g of sorbitan stearate and 80 mg of2,2′-azobis(2-methylbutyronitrile) were introduced into a 3000 ml flaskequipped with a stirrer and an apparatus for working under protectivegas, and the mixture was heated to 80° C. while stirring under a streamof nitrogen. After this temperature was reached, 200 g of acrylic acidwere added dropwise over the course of 2 hours and, separately, 80 ml ofcyclohexane and 320 mg of 2,2′-azobis(2-methylbutyronitrile) were addeddropwise over the course of 3 hours. After the addition of thepolymerization initiator was complete, the mixture was stirred at 80° C.for 3 hours. The product was then filtered off on a suction funnel anddried in a vacuum oven at 50° C. for 8 hours. 251 g of a white polymerpowder with a gel viscosity of 7 Pa·s were obtained.

Polymer 2

1320 ml of cyclohexane, 50 g of acrylic acid, 1.2 g of pentaerythritoltriallyl ether, 1.5 g of triglyceryl distearate and 80 mg of2,2′-azobis(2-methylbutyronitrile) were introduced into a 3000 ml flaskequipped with a stirrer and an apparatus for working under protectivegas, and the mixture was heated to 80° C. while stirring under a streamof nitrogen. After this temperature was reached, 200 g of acrylic acidand 6 g of triglyceryl distearate were added dropwise over the-course of2 hours and, separately, 80 ml of cyclohexane and 320 mg of2,2′-azobis(2-methylbutyronitrile) were added dropwise over the courseof 3 hours. After the addition of the polymerization initiator wascomplete, the mixture was stirred at 80° C. for 3 hours. The product wasthen filtered off on a suction funnel and dried in a vacuum oven at 50°C. for 8 hours. 251 g of a white polymer powder with a gel viscosity of7.5 Pa·s were obtained.

Polymer 3

1320 ml of cyclohexane, 50 g of acrylic acid, 1.5 g of pentaerythritoltriallyl ether, 80 mg of 2,2′-azobis(2-methylbutyronitrile) and 7.5 g ofa hydrogenated castor oil ethoxylate with 47 ethylene oxide units in themolecule were introduced into a 3000 ml flask equipped with a stirrerand an apparatus for working under protective gas, and the mixture washeated to 80° C. while stirring under a stream of nitrogen. After thistemperature was reached, 200 g of acrylic acid were added dropwise overthe course of 2 hours and, separately, 80 ml of cyclohexane and 320 mgof 2,2′-azobis(2-methylbutyronitrile) were added dropwise over thecourse of 3 hours. After the addition of the polymerization initiatorwas complete, the mixture was stirred at 80° C. for 3 hours. The productwas then filtered off on a suction funnel and dried in a vacuum oven at50° C. for 8 hours. 234 g of a white polymer powder with a gel viscosityof 11 Pa·s were obtained.

Polymer 4

A polymer was prepared from 250 g of acrylic acid, 1.5 g ofpentaerythritol triallyl ether and 7.5 g of sucrose stearate as for thepreparation of polymer 3. 255 g of a white polymer powder with a gelviscosity of 7 Pa·s were obtained.

Polymer 5

A polymer was prepared from 250 g of acrylic acid, 1.2 g ofpentaerythritol triallyl ether and 7.5 g of a cellulose ether with adegree of substitution of 46% and a viscosity of 0.1 Pa·s [measured in a5% strength solution in toluene/ethanol=4:1 (v/v) at 25° C., Ubbelohdeviscometer] as for the preparation of polymer 3. 243 g of a whitepolymer powder with a gel viscosity of 10.5 Pa·s were obtained.

Polymer 6

A polymer was prepared from 250 g of acrylic acid, 1.5 g ofpentaerythritol triallyl ether and 7.5 g of cetearyl polyglycoside asfor the preparation of polymer 3. 250 g of a white polymer powder with agel viscosity of 8.5 Pa·s were obtained.

Polymer 7

A polymer was prepared from 250 g of acrylic acid, 1.5 g of allylmethacrylate and 7.5 g of an ethylene oxide/propylene oxide blockcopolymer with a molecular weight of 2000 and a cloud point in water of23° C. as for the preparation of polymer 3. 247 g of a white polymerpowder with a gel viscosity of 7 Pa·s were obtained.

Polymer 8

A polymer was prepared from 250 g of acrylic acid, 1.5 g ofpentaerythritol triallyl ether and 7.5 g of a polystyrene/polyethyleneoxide block copolymer with a molecular weight of 2000 and astyrene/ethylene oxide ratio of 1:1 as for the preparation of polymer 3.253 g of a white polymer powder with a gel viscosity of 10 Pa·s wereobtained.

Polymer 9

A polymer was prepared from 250 g of acrylic acid, 1.2 g ofpentaerythritol triallyl ether and 7.5 g of sorbitan monolaurate as forthe preparation of polymer 3. 248 g of a white polymer powder with a gelviscosity of 8 Pa·s were obtained.

Polymer 10

A polymer was prepared from 250 g of acrylic acid, 1.2 g ofpentaerythritol triallyl ether and 12.5 g of a myristyl alcohol whichhad been reacted with 2.5 ethylene oxide and 5 propylene oxide units permolecule as for the preparation of polymer 3. 258 g of a white polymerpowder with a gel viscosity of 9 Pa·s were obtained.

Polymer 11

A polymer was prepared from 250 g of acrylic acid, 1.2 g ofpentaerythritol triallyl ether and 7.5 g of coconut fatty aciddiethanolamide as for the preparation of polymer 3. 234 g of a whitepolymer powder with a gel viscosity of 5 Pa·s were obtained.

Polymer 12

A polymer was prepared from 250 g of acrylic acid, 1.5 g ofpentaerythritol triallyl ether and 7.5 g of a polyoxyethylene sorbitanmonolaurate with a degree of ethoxylation of 20 as for the preparationof polymer 3. 252 g of a white polymer powder with a gel viscosity of 8Pa·s were obtained.

Comparative Example 1

1320 ml of cyclohexane, 50 g of acrylic acid, 0.3 g of pentaerythritoltriallyl ether and 80 mg of 2,2′-azobis(2-methylbutyronitrile) wereintroduced into a 3000 ml flask equipped with a stirrer and an apparatusfor working under protective gas, and the mixture was heated to 80° C.while stirring under a stream of nitrogen. After this temperature wasreached, 200 g of acrylic acid and 1.2 g of pentaerythritol triallylether were added dropwise over the course of 2 hours and, separately, 80ml of cyclohexane and 320 mg of 2,2′-azobis(2-methylbutyronitrile) wereadded dropwise over the course of 3 hours. After the addition of thepolymerization initiator was complete, the mixture was stirred at 80° C.for 3 hours. The product was then filtered off on a suction funnel anddried in a vacuum oven at 50° C. for 8 hours. 247 g of a white polymerpowder with a gel viscosity of 13 Pa·s were obtained.

Preparation and Assessment of Liquid Paraffin/Water Emulsions

0.4 g of polymer and 30 g of liquid paraffin are weighed into a 300 mlvessel and stirred until homogeneous. Then 103.6 ml of water are addedand-the mixture is stirred for 30 min. Finally, 0.4 g of triethanolamineis added and the mixture is stirred to give a preemulsified phase.Subsequently, the mixture is treated in a disperser until a homogeneouswhite emulsion with an average particle size of the emulsified oil phaseof less than 50 μm is produced. The emulsion is transferred into a 100ml measuring cylinder which is stoppered and stored at 25° C. for oneweek.

Emulsions 1-5 (Comparison with Prior Art)

Emulsions were prepared with the polymer from Comparative Example 1 andthe amount indicated below of a surfactant according to the statedmethod.

Emulsion 1: 12 mg of sorbitan stearate

Emulsion 2: 12 mg of hydrogenated castor oil ethoxylate with 47 ethyleneoxide units in the molecule

Emulsion 3: 12 mg of cetearyl polyglycoside

Emulsion 4: 12 mg of sorbitan monolaurate

Emulsion 5: 50 mg of sorbitan monolaurate

All the emulsions began to separate after 12-24 hours at the most andshowed two separate phases after 60 h at the most.

Examples 1-11

Emulsions were prepared with polymers 1-11 by the method indicatedabove. All the emulsions were still stable after 170 hours and showed notendency to separate.

Examples 12-18

Oil-in-water emulsions were prepared with polymer 3 by the statedmethod, using the following oils in place of liquid paraffin:

Example 12: Arachis oil

Example 13: Jojoba oil

Example 14: Capric acid triglyceride

Example 15: linear polydimethylsiloxane, viscosity 0.35 Pa·s

Example 16: Isostearic acid

Example 17: Decyl oleate

Example 18 Ethylhexanoic Ester of a C₁₆/C₁₈ Fatty Alcohol

All the emulsions were still stable after 170 hours and showed notendency to separate.

Examples 19-22

Liquid paraffin/water emulsions were prepared by the method indicatedabove using polymer 8 and replacing the amount of oil used by the statedamount:

Example 19: 15 g of liquid paraffin

Example 20: 45 g of liquid paraffin

An emulsion was prepared with polymer 8 by the stated method, replacingthe amount of polymer used by the stated amount:

Example 21: 0.27 g

Example 22: 0.53 g

All the emulsions were still stable after 170 hours and showed notendency to separate.

We claim:
 1. A process for stabilizing an oil-in-water emulsion whichprocess comprises adding to the emulsion from 0.01 to 5% by weight ofthe emulsion of a crosslinked copolymer obtained by precipitationpolymerization of a monomer mixture comprising: (a) monoethylenicallyunsaturated C₃-C₈-carboxylic acids, their anhydrides or mixtures of thecarboxylic acids and anhydrides, (b) compounds with at least 2non-conjugated ethylenic double bonds in the molecule as crosslinkersand, optionally, (c) other monoethylenically unsaturated monomers whichare copolymerizable with monomers (a) and (b), in the presence offree-radical polymerization initiators and from 0.1 to 20% by weight,based on the total weight of the monomers of a saturated, nonionicsurface-active compound.
 2. The process of claim 1, wherein thesaturated, nonionic surface-active compound is a member selected fromthe group consisting of sorbitan esters or sucrose esters or glycerolesters of saturated C₈-C₃₀-carboxylic acids, and alkoxylation productsof these esters.
 3. The process of claim 1, wherein the saturated,nonionic surface-active compound is a member selected from the groupconsisting of hydrophobically modified cellulose and hydrophobicallymodified starch.
 4. The process of claim 1, wherein the monomer mixturecomprises: a) 80-99.99% by weight of a member selected from the groupconsisting of acrylic acid, methacrylic acid, maleic acid, maleicanhydride, and methacrylic anhydride, and b) 0.01-20% by weight of amember selected from the group consisting of pentaerythritol triallylether, diacrylates or dimethacrylates of glycols or polyethylene glycolswith molecular weights up to 2000, pentaallylsucrose, allylmethacrylate, trimethylolpropane diallyl ether, andmethylenedisacrylamide.
 5. The process of claim 1, wherein theoil-in-water emulsion is a cosmetic or pharmaceutical oil-in-wateremulsion.